The Supreme Court ruled on Thursday the Clean Water Act applies to pollution that flows through groundwater into a major body of water rather than directly from a precise source, like a pipe or well, delivering a victory to environmentalists in a potentially landmark case.

In a 6-3 decision, the court sent the case, County of Maui v. Hawai’i Wildlife Fund, back to the U.S. Court of Appeals for the 9th Circuit.

Writing for the majority, Justice Stephen Breyer said the CWA, the country’s bedrock water law, requires a permit for pollution sources that amount to the “functional equivalent of a direct discharge.” Chief Justice John Roberts and Justices Ruth Bader Ginsburg, Elena Kagan, Brett Kavanaugh and Sonia Sotomayor joined Breyer in the decision, although Kavanaugh wrote a separate opinion.

[Pollution in paradise reaches high court with high stakes]

The case, which turns on the scope of that law and how pollution travels from its origins into a water source, could affect polluting industries, including mining, utilities and large ranching and agricultural operators.

Its ruling arrived days after the Trump administration printed in the Federal Register its finalized proposal to narrow the definition of what are considered “Waters of the United States,” or WOTUS — the rivers, lakes, streams and ponds under federal jurisdiction through the CWA.

In Maui v. Hawai’i Wildlife Fund, environmental groups sued the county in 2012, arguing wastewater from a water treatment plant violated the Clean Water Act and had damaged coral reefs nearby.

“This is a huge win, a huge win, for people who are concerned about protecting the waters across America,” said David Henkin, an Earthjustice attorney in Hawaii who argued the case against the county. 

At oral arguments in November, attorneys for the county told the court that Maui didn’t need a federal permit because the plant’s wastewater seeps into the Pacific Ocean through groundwater rather than flowing directly from injection wells.

The treatment complex discharges millions of gallons of wastewater every day and a federal tracer-dye study demonstrated much of that water trickles into the ocean.

Environmental groups warned a ruling for the county could create a shortcut for polluting industries to skirt the law, saying facilities would simply reposition their pipes so they don’t channel polluted material directly into water bodies. A silver-mining company in Ouray, Colorado, tried to use the tactic by moving its piping. A state agency denied that attempt in 2016.

Breyer wrote that federal lawmakers had not meant to establish a loophole. “We do not see how Congress could have intended to create such a large and obvious loophole in one of the key regulatory innovations of the Clean Water Act,” the court’s opinion reads. 

A group of 16 Republican senators filed a brief with the court, arguing lower-court rulings were too broad. 

Several fossil energy companies, including Kinder Morgan and Energy Transfer Partners, which manage pipelines, as well as the Edison Electric Institute, a trade group for electric utility firms that also stand to benefit from a weakened permitting process, filed briefs in support of Maui, too.

The Trump administration sided with the county, arguing the CWA does not apply to waste that moves through groundwater, reversing the position the EPA had held for decades under administrations of both political parties.

“This is the Trump administration versus Bush 1, Bush 2, Clinton, Obama,” Henkin said of previous presidencies and their administration’s positions. “This has been the consistent position of EPA going back 30 years,” he said. “We’re thrilled with the court’s ruling today, and we think that the fact that it’s a six-member majority, just sent the clear signal to the American people that we’re serious about protecting our waters.

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